Not Applicable.
1. Field of the Invention
The present invention is directed generally to a magnetic device and, more particularly, to a magnetic device that may be used for memory and logic circuits, and a method of forming such a device.
2. Description of the Background
Magnetic devices, such as magnetic memory devices, can be generally divided into two types of operation modes in terms of magnetization configurations in the device. Those types are linear and circular.
In linear devices, magnetization in a magnetic element is essentially linearly aligned. Examples of such devices include spin valve devices, pseudo-spin valve devices, and synthetic anti-ferromagnetic biased magnetic tunneling junction devices. One problem with linear operation is that the magnetization is discontinuous at the ends of the element. The ends introduce many kinds of end domains, yield variations in the switching processes, and yield variations of the switching field. As a result, linear devices are often unreliable in their operation.
Circular devices are typically solid circles (discs) or annular shaped elements (rings). The circular geometry results in a circular magnetization configuration and, therefore, the end domains are eliminated. The circular domain configurations are well defined and stable. In conventional thought, a circular magnetization configuration can be reversed with a circular magnetic field with an opposite polarity. In practice, however, using a circular magnetic field to reverse the polarity of the magnetization circulation in a circular magnetic device often generates incomplete reversal, leaving residual magnetic domains in the device.
Therefore, the need exists for a magnetic device that does not suffer from unreliability problems associated with linear devices, and one in which the state can be reliably changed without incomplete reversals typically associated with circular devices.
The present invention is directed to a device including a magnetic material having a magnetization configuration that is circular in a plane, and a word line for producing a magnetic field in the plane, the magnetic field being radial with respect to a point in the plane and within the circular magnetization configuration. The device may be, for example, a memory device or a logic device, such as a transistor.
The present invention solves problems experienced with the prior art because it provides for a well defined and stable state, and its state can be easily and completely changed when so desired. In addition, when embodied as a memory device, it does not need to be refreshed (unlike DRAM) and it requires very low current (unlike SRAM). When embodied as a logic circuit, the present invention does not require input signals to be maintained in order maintain the proper output signal. Those and other advantages and benefits of the present invention will become apparent from the description of the preferred embodiments hereinbelow.